package com.lagou.sqlSession;

import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;

import java.lang.reflect.*;
import java.util.List;

public class DefaultSqlSession implements SqlSession {

  private final Configuration configuration;

  public DefaultSqlSession(Configuration configuration) {
    this.configuration = configuration;
  }

  @Override
  public <E> List<E> selectList(String statementid, Object... params) throws Exception {

    // 将要去完成对simpleExecutor里的query方法的调用
    simpleExecutor simpleExecutor = new simpleExecutor();
    MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);
    List<Object> list = simpleExecutor.query(configuration, mappedStatement, params);

    return (List<E>) list;
  }

  public <E> List<E> queryListAndPage(String statementid, Object... params) throws Exception {
    MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);
    simpleExecutor simpleExecutor = new simpleExecutor();
    List<Object> query = simpleExecutor.query(configuration, mappedStatement, params);
    return (List<E>) query;
  }

  @Override
  public <T> T selectOne(String statementid, Object... params) throws Exception {
    List<Object> objects = selectList(statementid, params);
    if (objects.size() == 1) {
      return (T) objects.get(0);
    } else {
      throw new RuntimeException("查询结果为空或者返回结果过多");
    }
  }

  @Override
  public int insert(String statementid, Object... params) throws Exception {
    simpleExecutor simpleExecutor = new simpleExecutor();
    MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);

    return simpleExecutor.insert(configuration,mappedStatement,params);
  }

  @Override
  public int update(String statementid, Object... params)throws Exception  {
    simpleExecutor simpleExecutor = new simpleExecutor();
    MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);

    return simpleExecutor.update(configuration,mappedStatement,params);
  }

  @Override
  public int delete(String statementid, Object... params)throws Exception  {
    simpleExecutor simpleExecutor = new simpleExecutor();
    MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);

    return simpleExecutor.deleteById(configuration,mappedStatement,params);
  }

  @Override
  public <T> T getMapper(Class<?> mapperClass) {
    // 使用JDK动态代理来为Dao接口生成代理对象，并返回

    Object proxyInstance =
        Proxy.newProxyInstance(
            DefaultSqlSession.class.getClassLoader(),
            new Class[] {mapperClass},
            new InvocationHandler() {
              @Override
              public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                // 底层都还是去执行JDBC代码 //根据不同情况，来调用selctList或者selectOne
                // 准备参数 1：statmentid :sql语句的唯一标识：namespace.id= 接口全限定名.方法名
                // 方法名：findAll
                String methodName = method.getName();
                String className = method.getDeclaringClass().getName();

                String statementId = className + "." + methodName;
                MappedStatement mappedStatement =
                    configuration.getMappedStatementMap().get(statementId);
                String signature = mappedStatement.getSignature();
                // 准备参数2：params:args
                // 获取被调用方法的返回值类型
                Type genericReturnType = method.getGenericReturnType();
                // 判断是否进行了 泛型类型参数化
                if (signature.equals("select") && genericReturnType instanceof ParameterizedType) {
                  List<Object> objects = selectList(statementId, args);
                  return objects;
                } else if (signature.equals("select")) {
                  return selectOne(statementId, args);
                } else if (signature.equals("update")) {
                  return update(statementId, args);
                } else if (signature.equals("insert")) {
                  return insert(statementId, args);
                } else if (signature.equals("delete")) {
                  return delete(statementId, args);
                }

                return null;
              }
            });

    return (T) proxyInstance;
  }
}
